Presence of heme degrading enzymes in adult worms of Schistosoma japonicum

WEN-QI Liu¹ YONG-LONG Li¹ and Andreas RUPPEL^2
1Department of Parasitology, Tongji Medical College, Huazhong University of Science and Technology
²Institute of Tropical Hygiene, University of Heidelberg

Schistosome digests host erythrocyte hemoglobin to produce globin as the main source of nutriment, heme was considered to be released as the by-product of the catabolism of hemoglobin in the parasite, heme or heme analogs of high concentration are potential toxic for the parasite itself as well as the host. Heme oxygenase (HO) and biliverdin reductase (BR), the enzymes of heme degradation, have been detected in almost all species of eukaryotes. The presences of HO and BR have been proved in some protozoan parasites like Plasmodia and Leishmania, the presence of HO in Filarial Setaria digitata has been also reported recently. In present study, the extract of the adult worm of Schistosoma japonicum was investigated by enzymatic assays of HO and BR using commercial substrates hemin and biliverdin. The specific activities of HO and BR were 60.1 nmol bilirubin /mg/min and 52.2 nmol bilirubin/mg/min respectively, the activities of both enzymes were optimal at pH 8.7 and the rate of reactions came to the peak at 15min of incubation for HO and BR enzymatic reactions. The findings of present study suggest the presence of specific activity of heme catabolic enzymes in S.japonicum for the first time. At present, it is difficult to assign any other vital functions to HO of schistosome, however, it is inferable that the presence of heme degrading enzyme system and its catabolite(s) may be involved detoxification of the parasite in host.

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created 21/12/00